(If the stores were different sizes, we would need to analyze our data with two-way ANOVA, which I’ll discuss in Chapter 51, “Randomized Blocks and Two-Way ANOVA.”) This assumption allows us to use one-way ANOVA because we believe that at most one factor (the position of the display in the computer book section) is affecting sales. We assume that the 12 stores have similar sales patterns and are approximately the same size. Does the data indicate that the location of the books has a significant effect on sales? Resulting sales are contained in the Signif worksheet in the file Onewayanova.xlsx, which is shown in Figure 50-1. At 5 stores, the books were placed in the front at 4 stores, in the back and at 3 stores, in the middle. Weekly sales (in hundreds) were monitored at 12 different stores. The publishing company wants to know whether its books sell better when a display is set up in the front, back, or middle of the computer book section. If the p-value is greater than 0.15, the null hypothesis is true (the populations have identical means). If the p-value computed by Excel is small (usually less than or equal to 0.15), we can conclude that the alternative hypothesis is true (the means are significantly different).
To test these hypotheses in Microsoft Office Excel 2007, we can use the Anova: Single Factor option in the Data Analysis dialog box. Null hypothesis, which indicates that the means of all groups are identical.Īlternative hypothesis, which indicates that there is a statistically significant difference between the groups’ means. In analyzing the data, we can choose between two hypotheses: In the examples given above, the factors are the doctors, the container size, and the drug, respectively. When you’re trying to determine whether the means in several sets of data that depend on one factor are significantly different, one-way analysis of variance, or ANOVA, is the correct tool to use. Is there a significant difference in the length of time that four doctors keep mothers in the hospital after they give birth?ĭoes the production yield for a new drug depend on whether the size of the container in which the drug is produced is large, small, or medium?ĭoes the drop in blood pressure attained after taking one of four drugs depend on the drug taken? We often have several different groups of people or items and want to determine whether data about the groups differs significantly. How can I use the results of one-way ANOVA for forecasting? If I am determining whether populations have significantly different means, why is the technique called analysis of variance? More specifically, does it really matter whether the books are placed in the front, back, or middle of the computer book section? The owner of my company, which publishes computer books, wants to know whether the position of our books in the computer book section of bookstores influences sales.
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